/Engine/Plugins/Developer/Concert/ConcertMain/Source/ConcertServer/Public/IConcertServer.h
Callback when a message has been acknowledged by a remote endpoint
[FOnConcertMessageAcknowledgementReceivedFromLocalEndpoint](API\Plugins\ConcertTransport\FOnConcertMessag-) & OnConcertMessageAcknowledgementReceived()